The present invention relates to a process for recovering, at a reception end of a transmission path for digital data streams, data transmitted over the transmission path from a transmission end to the reception end.
In the present invention, various data are coded at the transmission end of the transmission path by means of a binary code word. The binary code word is generated by a code-word generator. The auto-correlation of the binary code word produces a Dirac Pulse. The various data at the transmission end of the transmission path are also coded with further binary code words produced by cyclically shifting the code word and by inverting the code word and further code words.
Further, in the present invention, the code word received is cross-correlated at the reception end of the transmission path by means of a cross-correlator to decode the code word. The relative position and the sign of the main maximum of the corresponding cross-correlation function is used to recover the data sent over the transmission path.
In a known process of this type ("telcom report" 14 (1991), No. 2, pages 104 to 107), a 2.sup.5 -m sequence is used as binary code word. This 2.sup.5 -m sequence has the property that the auto-correlation of this 2.sup.5 -m sequence produces an ideal Dirac impulse. From the 2.sup.5 -m sequence, further binary code words are produced by cyclically shifting the binary code word. These further binary code words are characterized by phases which differ from each other. In this way, 31 different data words can be coded on the transmission end, and thus 4-bit data words can be coded. 5-bit data words cannot be coded since only 31 code words are available. One embodiment of the known process, which constitutes an improvement with respect to the number of codable data words, uses inverted binary 2.sup.5 -m sequences on the transmission end in addition to the coding. In this way, coding a maximum of an additional 31 different data words is possible. As a whole, 5-bit data words can thus be transmitted and recovered on the reception end of a transmission path by cross-correlation, despite disturbances on the transmission path, if not more than 7 bit errors occur upon the transmission.
The object of the present invention is to develop the above process so that a comparatively large number of data present on the transmission end can be reliably recovered on the reception end.